1. Field of the invention
This invention relates to an interchangeable lens and an interchangeable lens system of the type in which information is exchanged between the lens and a camera.
Description of the Related Art
In a conventional interchangeable lens system, a controlled system of a lens unit is designed to have always the same configuration regardless of the types of lens employed. Furthermore, variations in the characteristics of the individual controlled systems which occur during the mass production are coped with by sorting parts having characteristics conforming to the standard.
However, the above-described conventional methods reduce mass production yield because of strict standards, thereby decreasing productivity. Further, technical restrictions created when an old type lens is designed are imposed on the design of a new type lens, preventing optimal design of the new type lens.
Further, in a conventional video camera, a diaphragm is controlled using an aperture value detected in an operated state of the camera by a sensor, such as a Hall element, provided at the diaphragm of the lens.
In the case of a video camera of the type in which a lens and a camera body are formed as one unit, an aperture value detection signal is transmitted from the lens to the camera body in the form of an analog signal.
In the case of a video camera of the type in which the lens can be detached from the camera body, a detection signal is converted into a digital signal by an A/D converter, and the digital signal is transferred to the camera body.
However, the quantization level at which the detection signal is converted into a digital signal may differ depending on the characteristics of the interchangeable lens employed, and this causes detrimental effects on the compatibility of the interchangeable lens system.
Furthermore, an interchangeable lens system which is adapted to a VTR or the like has its own exposure adjustment mechanism. This means that the exposure standard value of the lens, the dynamic range of an exposure signal or the like generated by a control circuit of the camera body vary in a wide range depending on the type of the lens employed. In consequence, sufficient compatibility of the lens control information cannot be ensured, this leading to the generation of automatic exposure adjustment errors.
In the control method in which digital communication is performed between a lens and a camera body, there is a possibility of delay in control or hunting.